@martinedcense Looking through all your posts, you seem to be making a regular habit of simply cutting and pasting other members comments rather than adding any of your own, this being mine made in post #3. Reported as spamming.Both Fiido D21 and X are torque sensor bikes, the X (according to one member here) having a higher quality branded torque sensor than the generic one fitted to the D21. The other main improvement is that the X also has hydraulic disc brakes rather than mechanical.